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Show 142 PROF. G. B. HOWES AND W. RIDEWOOD ON [Mar. 6, Wiedersheim and his pupil Kehrer, and of Baur (1), have added considerably to our knowledge of the limb-skeleton of the Urodela, that of the Anura has received much less attention. The most important investigations recorded since the classic of Gegenbaur (18), are those of Born (3, 5). Briihl has published (11) figures of a somewhat extraordinary character, pertaining to some seven or eight genera ; but concerning these we have little to say, except that we fully endorse Born's criticisms and corrections of them (6, pp. 48 et seq.). Born's latest communication purports to be somewhat revolutionary, so far at least as the carpus is concerned (6, p. 62). It will be seen, however, in the sequel, that we are unable to accept his determinations; and as the discovery of new elements and relationships has led us to differ from most of our predecessors, in our estimate of the morphological value of leading elements of both carpus and tarsus, it is binding upon us to preface this paper with an account of those observations upon which our dissensions are based. In accordance, then, with the exigencies of the case, we shall divide the paper into two sections : viz.:-firstly, a general part, in which will be given a review of the morphology of the carpal and tarsal elements, together with a detailed account of those hitherto unrecognized structures, whose discovery has necessitated a redetermination of the value of airy one or more constituents ; and, secondly, a special part, in which the leading families will be taken successively, the characters of the carpus and tarsus of each being noted in the light of the preceding section, and special peculiarities dealt with. b. Nomenclature.-Our investigations do not profess to be exhaustive ; they leave much to be settled, and we have accordingly refrained from introducing a nomenclature which might embody a premature expression of homological relationships with the limbs of other animals. In dealing with elements whose morphological value remains in the least degree doubtful, we have, for these reasons, adopted the nomenclature of Ecker (17) as being the more empirical and better suited to our purpose than the alternative one of Duges (16). In describing the pre-hallux (calcar), we have, in order to facilitate comparison with the works of our predecessors, adopted the older system of nomenclature, calling the outermost digit the fifth, the innermost one the pre-hallux or calcar, and that next to it the hallux or first digit. New terms have been introduced only where unavoidable; and some of these are, for reasons already given, purely empirical. c. Material.-It will be seen, from the second part of the paper, that we have examined the limbs of 37 genera and 60 species- adequate representatives of all the leading families as defined by Boulenger (7), with the exception of the Dgscophidce, Dendrophry-niscidce, Amphignathodontidce, and Hemiphractidce. For these specimens our grateful acknowledgments are due mainly to Prof. Huxley, and to Mr. G. A. Boulenger of the Natural History Museum. To the last-named gentleman we are indebted for further |
